Semiconductor device including contact structure

Abstract

In the present invention, a contact layer formed of a material having an electron concentration of less than 1×1022 cm−3 is directly provided on a surface of a semiconductor crystal having an n-type conductivity with a band gap of 1.2 eV or less at room temperature. Consequently, the wave function penetration from the contact layer side to the semiconductor surface side is reduced. As a result, the formation of the energy barrier height·ϕB due to the Fermi level pinning phenomenon is much suppressed. It is possible to achieve the contact with a lower resistivity and with high ohmic properties.

The invention claimed is: 
     
       1. A semiconductor device comprising a contact structure in which a contact layer formed of a material having an electron concentration of less than 1×10 22  cm −3  is directly provided on a surface of a semiconductor crystal having an n-type conductivity with a band gap of 1.2 eV or less at room temperature,
 wherein a donor concentration of a surface region of the semiconductor crystal is 1×10 18  cm −3  or less. 
 
     
     
       2. The semiconductor device according to  claim 1 , wherein the semiconductor crystal is any one of Si, Ge, and a compound of Si and Ge (Si x Ge y ). 
     
     
       3. The semiconductor device according to  claim 1 , wherein the semiconductor crystal is Ge, and the contact layer is formed of a material containing, as a main component, a germanide of any one of Gd, Y, Ho, Er, and Yb, or Bi. 
     
     
       4. The semiconductor device according to  claim 1 , wherein the semiconductor crystal is Si, and the contact layer is formed of a material containing Bi as a main component. 
     
     
       5. The semiconductor device according to  claim 1 , wherein the semiconductor device includes a metal layer on the contact layer. 
     
     
       6. The semiconductor device according to  claim 1 , wherein the semiconductor device is an n-channel MOSFET in which the semiconductor crystal is Si or Ge.